Hood-type annealing furnace



Jan. 1, 1963 R. L. CORBETT ET AL &07 0

HO0D-TYPE ANNEALING FURNACE Filed se t. 9. 1957 4 sheets-sheet IN V ENTORS Rober# L. (Ea/162#- Jan. l, 1963 R. L. CORBETT ET AL 50 HOOD-TYPEANNEALING FURNACE Filed Sept. 9, 1957 4 Sheets-Sheet 2 BY/?obe f L.(bI-beft c//c l Jan. 1, 1963 R. L. CORBETT ETAL 9 HOOD-TYPE ANNEALINGFURNACE Filed Sept. 9. 1957 4 Sheets-Sheet 5 INVENTORS F/ a. 3. Rebe/fL. Cbrb A ober/ L. Corb e# o Jan. l, 1963 R.'L. CORBETT ETAL L HOOD-TYPEANNEALING FURNACE Patented Jan. l, 1963 3,071,500 HOOD-TYPE ANNEALINGFURNACE Robert L. Corbett, 22664 W. Lake Road, and Robert L. Corbett,Jr., 22732 W. Lake Road, both of Rocky River, Ohio Filed Sept. 9, 1957,Ser. No. 682307 3 Claims. (Ci. 148--13) Our invention relates generallyto annealing furnaces and in particular to self-scaling gas tight forcedcooler to be used 'with gas tight hood-cover type furnaces for theannealing of heavy charges in the form of strip coils, etc. and moreparticularly to gas tight, two-part, hoodcover type furnaces to be usedwith preferably self-scaling gas tight forced coolers for the anuealingof heavy charges in the form of strip coils, etc.

In furnaces of this type, which are generally of the radiant tube firedbell or hood cover type, heat is normally applied to the external sideof the cover and then transmitted through an inner sheet metal cover tothe coils. Hence, heat is applied in such structures to the coils solelyby radiation from the inner cover, except for such heat as may betransferred from the inner cover to other parts of the coils bycirculation of the gaseous medium or the protective atmosphere gaswithin the inner cover. Conversely, in such structures, cooling of thecoils, after the charge is annealed, is efected by the dissipation ofheat through the inner cover after the furnace is removed therefrom.

With furnaces of this prior art type, a single heating hood or furnaceis usually consecutively placed over a plurality of bases with innercovers in succession. Although, such practice represents an improvementover other prior art practices of heating and cooling a charge enclosedin an annealing box in a stationary furnace, considerable expense andtime is nevertheless required to raise the temperature of the charge andalternatively to cool the charge to the desired temperature with aresultant high cost of annealing in tons per hour. Hence, in order toreduce the initial and maintenance cost of inner covers and to Shortenthe heating and cooling cycles in using such hood-cover type furnaces,many proposals have been made, such as providing various type means forcirculating the atmosphere during heating and cooling the charge ininner or protective covers of the type mentioned, providing spacersbetween stacked coils forming the charge to assist in the absorption ofheating through the edges of the coil laps, i.e. aXially instead ofradially through successive thicknesses or laps. Corrugated inner covershave further been proposed to increase the radiating surface. Furtherdouble wall inner covers have been used in connection with recirculatingsystems.

` It is therefore an object of our invention to provide means tomaterially shorten the heating and cooling periods of the annealingcycle.

It is a further object of our invention to provide means wherebyeconomies of time as 'well as expense may be etfected in annealing heavycharges in the form of strip coils, etc.

It is a further object of our invention to provide an annealing furnacewhich can be used successively with a minimum number of bases and gastight forced cooling covers, thus increasing the output of annealeclmaterial with a minimum amount of floor space.

Another object of our invention is to provide improved means forself-scaling the gas tight forced cooling covers when these are employedin our invention and placed on the charged bases.

A still further object of our invention is to eliminate purging underinner covers, which is required before placing a furnace over an innercover with a cold charge.

A further object of our invention is to provide an improved annealingfurnace and cooling cover which may be used in the annealing of chargesand which will be highly efiicient and economical in use.

Still further objects of our invention and the invention itself willbecome more readily apparent from a -purview of the description whichfollows, in which description reference will be made to the accompanyingdrawings, illustrating a preferred embodiment thereof, in whichdrawings:

FIG. 1 is a vertical section through a circular twopart hood-cover typefurnace disposed upon a granular seal base;

FIG. 2 is a view similar to that of FIG. l showing the cover or upperportion of the two-part furnace of FIG. 1 removed therefrom, the innerliner of the forced cooler being lowered within the lower portion of thetwo-part furnace of FIG. l for the cooling cycle;

FIG. 3 :is a view showing the furnace of FIG. 1 being removed from thecharge covered by the inner liner of the forced cooler;

FIG. 4 is a Vertical sectional view taken through a circularself-scaling gas tight forced cooler with inner and outer granularsealed liners in position with the granular seal base trough associatedtherewith.

The furnace of our invention, as best illustrated in FIGS. 1 and 2, isof the welhknown type which is removably disposed on a preferablygranular seal-type portable base. Such furnace is novelly provided witha removable top 50 in the form illustrated in our invention, or saidfurnace may :be provided with a hinged top, for purposes later to bedescribed herein.

The hood proper 10 comprises said top St?, a bottom Sea and includes agas tight structural frame 12 and a ref'actory lining 13. Heating meansof any desired type may be mounted in the assembled hood. In the formshown in our invention, radiant tubes 14 extend vertically within thehood and are heated by the combustion of gas supplied.

The portable base 11 includes a gas tight structural fr-ame 15 and arefractory lining or hearth 16 having a cover plate lfia thereon. Acharge support plate 17 is carried at suitable elevation above thehearth on radial steel veins 18 and corrugated concentric rings 18a. Thesupport plate 17 has a central opening 41 therein disposed immediatelyabove an opening 41' in the hearth plate 16a. The base 11, asillustrated, is provided with a granular scaling trough 19 to bepenetrated by a sealing flange 24 carried by the heating hood. i

In the form of our invention shown in FIG. 1, a recirculating fan motor22 having a fan shaft 42 and fan blades 43 is positioned immediatelybelow the hearth 16 and centrally thereof and its shaft 42 is: adaptedto be projected through the opening 41' in the hearth wherefor itsblades may rotate within the central portion of the charge support plate17 immediately below the opening 41. Atmosphere gases entering throughan inlet conduit, indicated at 27, are therefore circulated from belowthe charge support plate 17 -upwardly through the space betwecn theradiant tubes and the coils 20 stacked coaxially on the support 17,which form the charge to be annealed.

The atmosphere gas is then circulated through coil separators 21disposed between the adjacent coils 20 and between the bottom coil andthe support plate 17 and the orfice plate Zla disposed on top of thecharge, then downwardly through the eyes 20b of the coils and thecentral opening 41 in the charge support plate 17 and thence thlroughthe atmosphere gas outlet conduit indicated at By this method ofcirculation, the atmosphere gas is brought repeatedly into intimatecontact with the radiant tubes 14 and the coils 20 which are alsosubjected to direct radiant heat from the tubes 14, since in this formof our invention no inner cover is used during heating of the charge.Hence the rate of transfer of heat to the charge is appreciablyaccelerated over that in prior art structures.

If preferred the use of the base fan 22 could be eliminated, whereforsuch direct radation from the radiant tubes ;14 to the charge Would begreatly increased, thus aiding in greater production.

After heating the charge, the upper portion of the furnace 50 is removedtherefrom. The upper portion 50 may be, as above related, completelyremovable from the lower portion of the furnace, as in the form shown inour invention in FIG. l where the upper portion 50 is providedpreferably with a granular scaling blade 51 and the lower portion 50a isprovided With preferably a granular sea1- ing trough 52 into which thesealing blade 51 carried by the upper portion 50 of the furnace isadapted to penetrate when the cover is locked by means of lifting links53, which may be used to lock the upper portion 50' of the furnace tothe lower portion 5011 when the same is in use as above described.

The upper portion, it will be noted, further carries transverseextending guide brackets 54 at various portions about its circumferencewhich are adapted to be disposed over a plurality of guide posts 55disposed -at a spaced distance about the outer periphery of the base 11,wherefore the furnace may be guided into position and the upper 'portionmay be securely seated upon the lower portion when the same are joined.

It will be noted that when the lifting links 53 are disposed in theposition indicated by dotted lines, that the said upper cover portion 50is easily removed from its assembled position with the furnace bylifting same by means of a crane lifting bail 56 secured centrally ofthe upper portion of said removable cover portion 50. The inner liner 23of the forced cooler is then lowered through the upper open end of thelower portion of the furnace over the charge, as best shown in FIG. 2,and said inner liner 23, which is a gas-tight cylindrical shell formedof either plain, corrugated or the like steel with granular seal trough59, is lowered by means 'of the crane hook lifting eye 58 thereof intoposition. The furnace cover 50 is then again secured to the lowerportion 0a of the furnace by lowering the same into seated positiontherewith and lowering the l-fting links 53 to the position shownWherefore the assembled furnace is securely locked. The entire furnaceis then removed from its association with the charge and forced coolerinner liner 23, as shown in FIG. 3.

The atmosphere inlet connection 2711 is adapted during the lowering ofthe inner liner 23 to quickly purge the inner *liner while being placedin position over the heated charge as shown in FIG. 2.

Referring now more particularly to 'FIG. 4, the forced ,cooler outerliner 60 is lowered into position over the inner liner after the furnaceis removed by means of the crane hook bail 61 to provide gas tightaccelerated cooling.

of the charge. This outer shell 29 is preferably provided with a motordriven suction type fan 30 coaxially mounted above a central aperture29a of its upper portion 29' and is provided with knee braces 31, whichserve as members for testing an outer ring of the portable base frame11. Knee braces 'also serve for supporting the gas tight apron 34 withscaling blades 19' and 59' to penetrate scaling troughs 19 and 59, thusforming a gas tight seal With inner liner 23 without manual scaling orattention after the extended guide brackets 54' which are adapted to bedisposed over guide posts 55 to properly join the forced cooler outerliner 60 with the inner liner granular scaling trough 59. A fan motorframe 35 is secured to the top of the cooler shell 60 as by rivets,bolts 35' or the like and is provided with vents therein to assist incooling the inner liner 23 adjacent the shell 60. A motor 70 for drivingthe fan 30 is preferably mounted at one side of the forced cooler 60adjacent the upper portion thereof and belt means 71 are driven therebyto drive the fan shaft 37.

It will thus be noted that in the annealing furnace of our invention,the heating cycle is considerably Shortened and greater production maybe achieved'by the direct heating of the charge due to the eliminationof an inner cover. V

Secondly, it will be noted that the inner liner of the forced cooler canbe placed over the heated charge with a two-part hood type furnace forprotecting the heated charge when removing the furnace and placing theouter liner of the forced cooler into position, thus producing brightannealed coils without the use of an inner cover during the heatingcycle.

Third, by providing an inner liner with a granula' sealing trough andthe outer liner of the forced cooler with a. gas tight apron havingsealing blades to penetrate the inner liner scaling trough and theportable base sealng trough will thus produce bright annealed charges-free from scale `or stains during the cooling cycle.

Fourth, by providing a cooler having fan means associated therewith, thecooling cycle is considerably expedited.

Fifth, by providing the inner liner with a scaling trough, eliminatesmanual sanding required when using an inner cover during the heatingcycle, also any possibilities of occasional sand disturbances in whichevent -the charge would be discolored requiring re-annealing.

Sixth, improved economics in time will be achieved by the successive useof the two-part furnaces and forced coolers with inner and outer linersand with a minimum number of bases wherefore the output will beincreased with a minimum of floor space, time and labor, together witheliminating excessive inner cover maintenance costs.

We are aware that certain improvements may be made in the :form of ourinvention herein illustrated and described, without however departingfrom the spirit of our invention or the scope of the rapp'ended cl aims.

*What we claim is:

1. The process of annealing a met-al of a strip coil comprising, insequential steps, .placirg a hood-type furnace over said charge andheating said charge to an annealing temperature, removing an uppermostportion of said furnace and exposing the strip coil to the atmosphe-rewhile leaving `a lower portion thereof protecti-vely `surrounding saidch arge, plac-ing :a cooling bell over said change within said lowerportion of the furnace, removing said lower portion of said fiurnace,and subsequently allowing said cooling bell to remain in place untilsaid charge has cooled.

2. The process of annealing a metal charge of a strip coi-l compr ising,in sequential steps, placing a hood-type furnace over said change andheating 'said charge to an annealing temperature, removing an upper-mostportion of said furnace and ex-posing the strip coil to the atmosphereWhile leaving a lower portion thereof protectively surrounding saidcharge, plaoing an unheated cooling cover bell over said charge withinsaid lower portion while concu-rrently purging said cooling bell,removing said lower portion of said furnace, and subsequently al lowingsaid cooling bell .to remain in place during the References Cited in thefile of this patent cooling Of said charge. UNITED STA E PATENTS 3. Theprocess of -annealng a metal charge of a strip T S coil comprising, insequential steps, placing a hood-type 1268685 Cooudge June 1918 furnaceover said charge and directly heating said charge 5 1534319 GanaghanJuly 1927 to `an annealing temperature, removing an uppermost 1367737Hatcher July 1932 portion of said furnace and expos-ing the strip coilto the 2278391 Munford 1942 atmosphere While leaving a lower portionthereof pro- 2781188 MCKOWH 1957 teotively surrounding said charge,placing an unheated 2303449 Ludwlg 1957 cooling bell over said chargewithin said lower portion of 10 FOREIGN PATENTS the furnace, removingsaid lower portion of said furnace i without removing said cooling bell,and encompassing x f said cooling bell With a forced air cooler wherebyair is rea n am u y caused to pass over the outer surface of saidcooling bell to rapidly cool said charge.

1. THE PROCESS OF ANNEALING A METAL OF A STRIP COIL COMPRISING, INSEQUENTIAL STEPS, PLACING A HOOD-TYPE FURNACE OVER SAID CHARGE ANDHEATING SAID CHARGE TO AN ANNEALING TEMPERATURE, REMOVING AN UPPERMOSTPORTION OF SAID FURNACE AND EXPOSING THE STRIP COIL TO THE ATMOSPHEREWHILE LEAVING A LOWER PORTION THEREOF PROTECTIVELY SURROUNDING SAIDCHARGE, PLACING A COOLING BELL OVER SAID CHARGE WITHIN SAID LOWERPORTION OF THE FURNACE, REMOVING SAID LOWER PORTION OF SAID FURNACE, ANDSUBSEQUENTLY ALLOWING SAID COOLING BELL TO REMAIN IN PLACE UNTIL SAIDCHARGE HAS COOLED.